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Abstract Throughout the halogen bonding literature, electron withdrawing groups are relied upon heavily for tuning the interaction strength between the halogen bond donor and acceptor; however, the interplay of electronic effects associated with various substituents is less of a focus. This work utilizes computational techniques to study the degree ofσ‐ andπ‐electron donating/accepting character of electron withdrawing groups in a prescribed set of halo‐alkyne, halo‐benzene, and halo‐ethynyl benzene halogen bond donors. We examine how these factors affect theσ‐hole magnitude of the donors as well as the binding strength of the corresponding complexes with an ammonia acceptor. Statistical analyses aid the interpretation of how these substituents influence the properties of the halogen bond donors and complexes, and show that the electron withdrawing groups that are bothσ‐ andπ‐electron accepting form the strongest halogen bond complexes.
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Photooxidation and Cleavage of Ethynylated 9,10-Dimethoxyanthracenes with Acid-Labile Ether Bonds
This paper describes a series of twelve 9,10-dimethoxyanthracene derivatives functionalized with a range of electronically diverse ethynyl substituents at the 2 and 6 positions, aimed at tuning their optoelectronic properties and reactivity with singlet oxygen (1O2). Optical spectroscopy, cyclic voltammetry, and density functional theory calculations reveal that the ethynyl groups decrease the HOMO-LUMO gaps of these acenes. Notably, bis(dimethylanilineethynyl) substituents increase the wavelength of absorbance onset by over 60 nm compared to 9,10-dimethoxyanthracene (DMA). Furthermore, all twelve molecules react with 1O2 through cycloaddition at the 9 and 10 positions to form endoperoxides. Although the presence of ethynyl groups decreases the reaction rates, they are at least 40% of the rate observed for DMA. Finally, these endoperoxides cleave to form quinones when exposed to protic acid. This behavior, combined with red-shifting of absorbance spectra, emphasizes their potential in photocleavable materials.
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- Award ID(s):
- 2003341
- PAR ID:
- 10621699
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- The Journal of Organic Chemistry
- Volume:
- 90
- Issue:
- 5
- ISSN:
- 0022-3263
- Page Range / eLocation ID:
- 1996-2007
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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